While 26 trillion emails will be sent across the world on a daily basis during 2007, into the future, usage is expected to plateau and, over time, to metamorphose.

According to IDC, increases in volume will only hit single figures because, on the one hand, the market is pretty much saturated and, on the other, users, especially the younger generation, are starting to rely increasingly on alternative collaboration tools, such as instant messaging (IM), voice over IP (VoIP) and blogs, to communicate and share information.

Of the 26 trillion emails flying around cyberspace each day, said Mark Levitt, IDC's program vice president for collaborative computing and the enterprise workplace, almost 11 trillion will comprise spam, 10.5 trillion will consist of person-to-person communications, and 4.5 trillion will be email alerts and notifications.

But just how is it that email has become so massive and where did it come from in the first place? Electronic mail, or email as it is now known, predates the internet and was, in fact, one of the "killer apps" that contributed to its current popularity.

The idea behind it first emerged in 1965 when various research institutions wrote the first text-message-exchange applications as a means of enabling users of time-sharing mainframes, which could run more than one application, to communicate with each other.

But the next big step towards a system that could be recognised today as email was made by Ray Tomlinson, a programmer at US acoustics consultancy Bolt Beranek and Newman.

Tomlinson had helped develop the Tenex operating system (OS), which later became one of the most popular PDP-10 OSs and included support for the Arpanet network control protocol. The Arpanet was developed by the US Department of Defense's Advanced Research Projects Agency (Arpa) and was the first operational packet-switching data network — the predecessor of the internet.

But in late 1971, Tomlinson wrote a file transfer program called CPYNet, which could copy and transfer files over the Arpanet, and added it to another application called SNDMSG.

SNDMSG had been written to send messages to other users of time-sharing mainframes, but Tomlinson now rewrote it to run on Tenex. He also chose the "@" symbol, which is still in use today, to combine both user and host names in order to extend addressing to the network. This meant that, for the first time, it was possible to send simple transactional messages to users working on different hosts connected to the Arpanet.

While the medium continued to evolve over the next couple of decades, it wasn't until 1988 that email went commercial. This happened courtesy of Vint Cerf, who had worked on the Arpanet, helped develop the TCP/IP protocol and was one of the founding fathers of the current-day internet.

At the time, however, he was vice president of MCI Digital Information Services. Through the Corporation for National Research Initiatives, a non-profit organisation set up to develop network-based information technologies, Cerf arranged to connect the company's internal email system, MCI Mail, to the National Science Foundation's NSFNet for "experimental" purposes.

The NSFNet was a TCP/IP-based network that enabled academic researchers to access five supercomputing centres in the US, and the move constituted the first commercial use of the internet for email.

Five years later, however, large network service providers America Online and Delphi followed suit and also connected their proprietary email system offerings to the internet — a move that kick-started the wide-scale adoption of online email as a crucial business and personal communications tool that has, to some extent, replaced voice.

But just because email in its current form is wildly popular does not mean to say that it will retain its dominance forever or that its usage will remain the same.

Matt Cain, lead email analyst at Gartner, for one, predicts that the medium will evolve over the next few years in four key ways. Firstly, he anticipates that access will become almost ubiquitous, with users increasingly expecting to access their email via any web browser on any mobile device instantly, particularly as wireless networks become ever more widespread.

Secondly, organisations will start to segment their email users and provide different groups with access to different levels of service in a bid to cut costs. While a typical Microsoft Exchange account costs about $10 (£5) per user, per month, companies are already starting to explore cheaper options for light users, such as factory workers or data-input clerks.

"But this can be a mixed blessing because of the administration costs," Cain warned. "The history of email over the last decade has been that most organisations are trying to get down to a single email system, but we're seeing that start to change now."

The third trend relates to a growing move to managed email services. While the adoption of this model currently accounts for less than five percent of the total market...

...not least because such services are currently more expensive than equivalent on-premises offerings, this situation is expected to alter as prices come down.

The final piece in the jigsaw is increasing demand for email management systems as a result of the growing regulatory burden. This has led to a rising interest in records management, which includes emails, not least in case audit trails of business activity are required by a court of law.

Into the longer term, however, the use of email is expected to flatten out and change, although it will not go away — just as paper and voicemail hasn't.

Clive Longbottom, a service director at Quocirca, explained: "The massive usage of email as a personal means of communication will plateau as users move more towards IM, VoIP, web-sharing and Web 2.0, such as social-networking sites. Within the business sphere, it'll tend to revert to a more formal usage for the exchange of documents needed for things like contract negotiation and as a one-to-many distribution system."

But this does not necessarily mean to say that email will lose its popularity, simply that it will become one text communication tool of many as the number of interactions and the modalities users employ to perform different tasks increases.

As a result, the challenge for users will be to determine which of the modalities is the most appropriate for the task in hand, while organisations will need to get to grips with how to best exploit this growing communications literacy for business purposes.

But vendors such as IBM and Microsoft are already jumping on this particular bandwagon by assembling collaboration platforms for information workers. These comprise a unified set of software services, which include messaging capabilities, such as email and calendaring; team collaboration, such as work spaces and document repositories; real-time communications, such as IM and videoconferencing; and social-networking tools, such as blogs and wikis.

"The important thing is that they won't be discrete communications modalities but will bleed into each other, and the idea of presence is the key here, so you can see where people are. Currently the notion of deploying or managing these modalities in a unified fashion is fairly rudimentary, but we're at the start of a drive to unified communications, which will take about five years," said Cain.

Nonetheless, a study by Forrester Research indicates that 60 percent of the businesses that it surveyed in North America and Europe have such unified communications technology on their agenda for 2007, with nine percent identifying it as a critical priority.

But, while the range of communications modalities is unlikely to increase hugely, such tools will increasingly be integrated into business applications to provide contextual collaboration capabilities. This means that users will not need to toggle, for example, from their ERP package to their email box, as such functionality will be embedded.

Another important element of the ultimate vision, meanwhile, is that users have a single address to which messages are sent and received in appropriate format using a range of different software and devices.

Erica Driver, a principal analyst at Forrester, explained: "Email will become more unified with other forms of collaboration, meaning that a voicemail will turn into an email, or an instant message will turn into an email, based on user profiles and other criteria, like whether someone is in an important meeting."

This morphing of modalities means that the distinction between tools such as IM and email will start to blur, leading to the creation of a more seamless continuum.

For this to take place, however, there needs to be a much more integrated use of presence than is currently the case. One of the challenges here is that vendors persist in implementing presence protocols, such as SIP, in their own unique way to suit their own ends rather than those of the wider market.

Christopher Harris-Jones, a principal analyst at Ovum, explained: "The problem is that this requires agreement on standards across multiple industry sectors, but getting agreement across even one is a nightmare. At the moment, you can't even use different IM systems to communicate, so getting IM and SMS unified, for example, won't happen tomorrow."

Nonetheless, he believes that it is only a matter of time before such convergence will take place. "Email will remain a major and important method of communications, but it's a very exciting time and things are changing — and quickly," he concluded.